1. Field of the Invention
The present invention relates to an adaptive universal multimedia access (UMA) system of user equipment for multimedia resource in an Internet protocol multimedia subsystem (IMS) environment.
2. Description of the Related Art
Various IP based multimedia services are provided to a notebook environment and a personal digital assistant (PDA) environment based on a wireless local area network (WLAN). Accordingly, various researches are actively in progress to graft a mobile communication technology onto an IP based environment.
An Internet protocol multimedia subsystem (IMS) is a representative one among the introduced method of grafting the mobile communication technology onto the IP based environment. The IMS was introduced by the 3rd generation partnership project (3GPP) which is the European 3rd generation mobile communication standard. The IMS discloses a method of receiving an IP based service through a wireless communication terminal such as a mobile phone or a cellular phone.
The IMS allows the wireless communication terminal to receive various visual communication services such as a visual communication, a video chatting and a video conference and to use a game service, which include not only voice service but also image or graphic services.
Hereinafter, the Internet protocol (IP) multimedia subsystem (IMS) environment will be briefly described.
The IMS is a communication standard introduced by the 3rd generation partnership project (3GPP) to support various services by connecting a wireless mobile communication terminal to an IP network capable of providing plenty of services.
The IMS defines how to connect terminals to the IP network through a server and how to select a server to connect the terminals to the IP network. That is, the IMS defines components and sequence of processes required to connect the terminals to the IP network.
FIG. 1 is a schematic diagram of an IP multimedia subsystem (IMS).
Referring to FIG. 1, the IMS includes an application server 10, a home subscriber server (HSS) 20, a call session control function (CSCF) 30, a mobile communication network (3G)/general packet radio service (GPRS)/CDMA 40, a user equipment (UE) 50, a media gateway control function (MGCF) 60, a media gateway (MGW) 70 and a public switched telephone network (PSTN) 80.
The HSS 20 is a master database for a user. That is, the HSS 20 stores information of subscribers and provides information of corresponding subscriber according to a request.
The CSCF 30 controls a gateway and an incoming call, manages serving profiles and performs operations for address processing. According to the functions, the CSCF 30 is divided into a proxy-CSCF (P-CSCF), an interrogating-CSCF (I-CSCF) and a serving-CSCF.
The P-SCSF functions as a connecting point when the UE 50 accesses the IMS through the GPRS 40.
The I-SCSF functions as a connecting point for delivering all incoming calls to subscribers in the own network and as a connecting point for connecting the subscribers in the own network to subscribers in other network. The I-CSCF selects the S-SCSF by inquiring corresponding information to the HSS 20 and allocates the S-CSCF to the UE 50 while registering.
The S-CSCF performs major functions for processing calls.
The MGCF 60 performs a signaling transformation on data transmitted from the external PSTN 80 to the IMS and forwards a transformed request message to the S-SCSF. Also, the MGCF 60 controls the MGW 70.
The MGW 70 functions for connecting the wireless terminals to the PSTN 80. In order to cooperate with the PSTN 80, the MGW 70 transcodes an IP packet type media data for the IMS to a predetermined format suitable for the PSTN 80.
A gateway GPRS system node (GGSN) 41 is a gateway between a wireless switching network and an Internet network so that a wireless terminal transmits/receives data to/from a destination in the general Internet network through the wireless switching network having a base station. A serving GPRS support node (SGSN) 42 traces a mobile node and performs operations as a tunnel exchanging a packet with the GGSN.
Terminals in the IMS shown in FIG. 1 are allowed to connect different home networks. That is, the terminals and the home network are connected through a mobile communication network, GGSN 41 and SGSN 42. In order to communicate with other terminal, a session is connected at first. After connecting the session, the terminals transmit and receive data one another.
As illustrated in FIG. 1, the transmitting terminal 50 includes an application 51 related to mobile communication, a protocol stack 52 for performing a sequence of control operations for communication control, a transmitting/receiving module 53 for transmitting/receiving data, a codec 54 for encoding/decoding data, and a display 55.
The protocol stack 52 includes a session initialization protocol (SIP) for connecting a session and a protocol stack configured of a real time transport protocol (RTP)/real time control protocol (RTCP), a user datagram protocol (UDP)/transmission control protocol(TCP) and an Internet protocol (IP) for transmitting media. Since these protocol stacks are well known to those skilled in the art, a detail description thereof will be omitted.
In the IMS environment illustrated in FIG. 1, the UE 50, i.e., a mobile terminal, accesses to the CSCF 30 that is an interface of an IP core network using the GGSN41/SGSN42 of a related art mobile communication network. The UE 50 receives various services from the IP core network by cooperating with the application servers 10 providing various applications and the HSS 20 managing user information as a database through the CSCF 30. Since the IMS specification document describes detail information of each component, a detail description thereof will be omitted.
The standard introduces a basic architecture as described above. For example, the standard defines specifications about signaling with the CSCF 30. Specifications about application are not well defined in the standard. That is, the application is developed according to each developer.
Mobile terminals are manufactured with various sizes of displays from a size of 128×96 to a size of 640×480 that is VGA level display. Also, mobile terminals are manufactured to include various types of decoders to recover and reproduce audio or video data. For example, as a standard for image data, MPEG1, MPEG2, MPEG4, H.263 and H.264 are used. As a standard for audio data, G.711, G.726, audio modem riser (ARM), advanced audio codec, and MPEG1 layer 3 (MP3) are used.
However, the mobile terminal cannot include all of standard decoders because of limited resources. The mobile terminal generally includes predetermined decoders selected by the manufacturer. Some of mobile terminal may include non-standard CODEC. Therefore, mobile terminals manufactured for different mobile communication service providers are not comparable one another. If a spec of transmitting terminal and a spec of receiving terminal are different, there is a problem arisen to reproduce multimedia data from one terminal at other terminal. For example, if the transmitting terminal has a better spec than the receiving terminal, the receiving terminal cannot reproduce the multimedia data transmitted from the transmitting terminal to display image data or to reproduce audio data.
If the transmitting terminal transmits image data based on a QVGA resolution, 320×240, and the receiving terminal supports only a QCIF resolution, 176×144, then the receiving terminal cannot display the image data transmitted from the transmitting terminal. Accordingly, the receiving terminal wastes it's resource to receive useless image data.
As another example, if the transmitting terminal records a QVGA level of moving image at 30 fps and transmits the recorded moving image to the receiving terminal supporting only a QVGA level of moving image at 7.5 fps, the receiving terminal displays the moving image transmitted from the transmitting terminal in a four times slower speed because the receiving terminal has ¼ performance of reproducing the moving image compared to the transmitting terminal.